The present invention relates to a device for supplying energy from a railroad mains producing alternating or direct voltages at different levels to loads in a rail-bound vehicle. More particularly, the present invention relates to such a device including a static inverter equipped with thyristors and preceded by a rectifier, each thyristor of the inverter being equipped with an excess inverse voltage protection circuit (CR-R member) with the normally open contact of a relay being connected ahead of the inverter.
It is known to limit the inverse voltage of the thyristors of an inverter by equipping each of the thyristors with a CR-R member -- shown in FIG. 2 of the accompanied drawing and formed by capacitors 30, 31, 32-- and to connect a filter comprising a coil and a capacitor ahead of the inverter-- choke 6 and capacitor 7 in FIG. 1. This design has been state of the art for many years as can be seen from the illustrations on pp. 41, 47, and 272, Figures 41.1, 47.1, and 272.1 of the book "Thyristoren" by K. Heumann, C. Stumpe published by Teubner, Stuttgart, West Germany, 3rd Ed., 1974.
In such a protective circuit, it may happen that upon the occurrence of a rapid succession of a plurality of mains voltage peaks, the mains caused inverse voltage across the thyristors rises considerably so that the thyristors -- unless they have been overdimensioned-- are destroyed. If, however, a fuse or circuit breaker in the form of an overvoltage protector is connected ahead of the inverter, such a fuse would have to be changed very often.